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Birch Tree Allergy: Pollen is in the Air!

Do
you see them? The catkins on the birch trees are a sure sign of spring
and a warning to all those birch-allergic patients. The catkins are
those long pendulous structures drooping from the small branches. Each
male catkin can release 6 million pollen grains in a season! (it only takes a few hundred to trigger an allergic reaction)

Birch trees

Belong
to the Betula species. There are 50 species worldwide and 15 species
are native to North America. River Birch has the most southerly range.
The yellow birch tree is the largest Eastern birch found commonly in
Canada and the Northeastern U.S. In fact, birch trees are plentiful
from Alaska and Canada southward. These trees prefer to grow in direct
sunshine and not shade. Birches are rapidly growing but their lifespan
is relatively short at about 50 years. The bark is characteristically
thin with lenticels (dark horizontal lines). The leaves are
alternate, ovate (wider at one end) or triangular and doubly serrate
(notched or tooth like).

Birches
are used for wood pulp and lumber. Native Americans used birch bark to
make canoes and wigwams. Sap from the birch tree can be boiled to make
syrup or fermented to make an adult beverage (Birch beer).

Birch Pollen

Birch
trees are wind-pollinated. Pollen and seed catkins are on the same
tree. The male catkins are formed in late fall and appear as stiff
fingers on long shoots that elongate and become pendulous in the spring.
Birch trees release enormous amounts of pollen in the early spring.
This occurs just before the leaves unfold. Anthesis (time when
the flower is fully functional) occurs from February into May. Birch
pollen under the microscope is usually triporate (3 pores or holes).
Each grain is between 20 and 27 micrometers in size (1/1000 inch).
(This is about the size of a wool fiber or 3 times wider than a human
red blood cell)

The pollen can trigger spring time allergic rhinitis (hay fever) and even asthma.

Pollen-Food Allergy Syndrome:

Many individuals with birch pollen allergy will also experience mouth or throat itching and mild swelling when eating fresh apples.
This is due to the cross-reactive heat sensitive protein. When the
apple is cooked (apple pie or apple sauce), the protein is denatured
(broken down) and symptoms do not occur.

At Family Allergy Asthma & Sinus Care,
we enjoy teaching our patients the finer points of the triggers of
their allergies. You may even find yourself becoming interested in
botany (plant science). If you are suffering from spring allergies,
call us at 704-817-2022 and make an appointment.